The invention relates to a warp knitting machine in which the knitting elements and each warp beam are driven by their own electric motors, powered from a common network.
Such a drive for a warp knitting machine is described in German Pat. No. 30 25 782. That patent publication points out that when a power failure occurs in the network, the main shaft of the machine and the parts connected with it come to a standstill only after a certain delay, because of their mass, while the drive of the warp beam or the drives of the warp beams are stopped relatively quickly. This means that all of the warp yarns of all of the warp beams can break. To eliminate this danger, the cited patent publication describes a switching mechanism in which the main shaft of the machine is equipped with an electrically controlled brake which moves from its disengaged position to its braking position under the influence of a stored braking force. This results in the main shaft coming to a stand-still in much less time, almost jerkily, so that breaking of the warp yarns is avoided. Because of the considerable masses involved with the main shaft, this almost jerky braking of the main shaft imparts great stresses upon the machine parts, and this, in turn, can lead to internal shifting in the machine and even to damage. The patent publication also discusses this stressing of the machine, specifically by indicating an additional switch to disengage the above-described brake in case of a normal shut-down process, so that the almost jerky stopping of the main shaft is avoided in this normal procedure. It is, however, impossible to eliminate the stress to the machine which results in case of network power failure.
It should also be noted here that U.S. Pat. No. 2,625,021 discloses an electrically engaged clutch in connection with a warp knitting machine wherein the force which drives the warp beam is derived from the main shaft. Here, the setting of a more or less powerful slaving force via the clutch ensures the maintenance of thread tension at its normal level by imparting more or less powerful driving force to the warp beam when yarn tension is altered.